1. Field of the Invention
The present invention relates to a keyboard, and more particularly, to a keyboard comprising keys having improved sensitivity to operation.
2. Description of the Prior Art
A keyboard generally comprises several types of keys for executing different functions, such as alpha numeric keys for the input of various characters and hot keys (Tab key, Shift key, Space key, etc.) for executing specific functions. Generally, keys with different functions are of different size or shape, however, it is required that all the keycaps be pressed centrally to activate the switches. This is because, if the position to which pressure is applied is proximate to an edge of the keycap, the elastic contact body of the key may not deform properly to activate the switch, resulting in an ineffective operation of the key. This happens especially in the longer keys. As an ongoing trend toward compact electronic products, the input devices have become smaller and thinner, leading to a reduction in the stroke of the key. With the shorter stroke of the key, the switch may not be properly pressed to generate a corresponding signal when the user presses the keycap at a high speed. Such a drawback causes much inconvenience for the user.
To resolve the aforementioned drawback, there is provided a prior art keyboard 200, including: a membrane circuit board 40, a keycap 50 and a base plate 60. As shown in FIGS. 8A and 8B, the membrane circuit board 40 is disposed on top of the base plate 60 and comprises a plurality of switches 41; the keycap 50 is disposed on top of the membrane circuit board 40 and comprises a plurality of columnar bodies 51 perpendicular to the bottom surface thereof; the base plate 60 is provided with an opening 61 positioned at a location corresponding to one of the plurality of columnar bodies 51. When the user presses an edge of the keycap 50, one of the plurality of columnar bodies 51 located at the bottom surface of the keycap 50 will move downwardly to press the membrane circuit board 40, thereby one of the plurality of switches 41 of the membrane circuit board 40 can be turned on to generate a corresponding signal. As each columnar body 51 is arranged to be perpendicular to the bottom surface of the keycap 50, the area where the columnar body 51 is in contact with the membrane circuit board 40 is rather small. Accordingly, the pressure applied by the columnar body 51 is concentrated at certain area of the membrane circuit board 40, causing damages to the area which frequently receives pressure easily. In addition, a corner adjoining the base plate 60 and the opening 61, along which a portion of the membrane circuit board 40 dips into the opening 61 when being pressed by the columnar body 51, is right-angled so that creases are prone to be formed on the membrane circuit board 40, inflicting damages easily.
Therefore, it remains a problem to be solved in the art as to how the durability of the prior art membrane circuit board, which is damaged easily when being pressed frequently, could be improved.